Inverter Reactive Power Control for Volt-Var Instability
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Solution Overview
Problem
Inverter-based resources in wind farms face instability due to high gains in volt-var control, leading to oscillatory behavior in reactive power commands, which can destabilize operation during grid contingencies.
Innovation Solution
A method and system that monitor command signals for oscillatory behavior, filter and analyze them using wash-out filters and lag filters, and reduce the gains of the volt-var regulator to mitigate instability, while maintaining power output to the electrical grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high gains are used in the volt-var regulator to meet fast voltage regulation requirements, then voltage regulation speed is improved, but system stability deteriorates during grid contingencies
Solution Approach 1:
The patent applies dynamics by making the controller gains adjustable rather than fixed. The system dynamically adapts the proportional and integral gains of the volt-var regulator based on real-time stability assessment. When oscillatory behavior is detected, the gains are reduced to stabilize the system; when stability is adequate, the gains can be increased to improve response speed. This dynamic adaptation resolves the contradiction between fast regulation and stability.
Solution Approach 2:
The patent changes the parameters (gains) of the volt-var regulator based on system conditions. By monitoring oscillatory behavior and adjusting the proportional and integral gain parameters accordingly, the system can operate with high gains during stable conditions for fast regulation, and switch to lower gains during contingencies to maintain stability, thus resolving the trade-off between speed and stability.
2Stability of the object's composition
If the farm-level controller reduces gains to reduce instability, then system stability is improved, but voltage regulation performance deteriorates
Solution Approach 1:
The patent implements periodic assessment of system stability through monitoring oscillatory behavior in reactive power commands. The system continuously evaluates stability conditions and periodically adjusts the controller gains accordingly. This periodic action allows the system to maintain high performance during stable periods while ensuring stability during contingencies, resolving the contradiction between stability and performance.
Solution Approach 2:
The patent uses feedback by monitoring the reactive power command signals for oscillatory behavior and using this information to adjust the volt-var regulator gains. The feedback mechanism enables the system to detect instability conditions and respond by reducing gains to maintain stability, while allowing high gains during stable conditions to maintain good voltage regulation performance.
Data Source
AI summary
A method for controlling a power system having at least one inverter-based resource connected to an electrical grid includes monitoring, via at least one controller of the at least one inverter-based resource, one or more command signals issued by a system-level controller. The method also includes determining, via the at least one controller of the at least one inverter-based resource, whether the one or more command signals issued by the system-level controller includes oscillatory behavior characteristic of an instability. In response to determining that the one or more command signals issued by the system-level controller includes oscillatory behavior characteristic of the instability, the method includes reducing one or more gains of a volt-var regulator of the system-level controller to reduce the instability.